US2611086A - Antenna system - Google Patents

Description

Sept. 16, 1952 E. v. AMY l-:rAL

ANTENNA SYSTEM 3 Sheets-Sheet 1 Filed June 6. 194'? INVENTORS. ERA/57 l- AMY JUL/us 6. Activa-s E. V. AMY ET AL.

Sept. 16, 1952 ANTENNA SYSTEM 3 Sheets-Sheet 2 Filed June 6. 1947 INVENToRs \8o ERA/E57 V/JMY JUL/us G. Heft/E5 Fla@ Sept. 16, 1952 E. v. AMY Erm.

ANTENNA SYSTEM 5 Sheets-Sheet 5 Filed June 6, 1947 l ...MM 1

INVENTORS. ERNEST Y /IMY HTTORNEY comprises a pair of somewhat semi-circular' shells 24 (Fig. 3) which are bolted to the upperY end of the upright 23 and have coextensive attened upper ends 25. A strip of insulation 26, of a size to define the gap of dipole 2 I, is fastened to the projecting ends 25 of the shells, and the ends of the tubing of dipole 2| are flattened, as indicated at 21, and secured at the opposite ends of insulation 26. The upper leg of the dipole 2| may be braced by means of a clip 28 which is fastened at one end to the insulation strip 26 and has its upper end clampedaround the upper leg of the dipole, as shown at 29.

The lower dipole 22 comprises two opposed U- shaped sections 3| and 32, the end of which are flattened, with the ends of the upper legs of the sections overlapped, as seen at 33 (Fig. 2), and suitably bolted or secured to the upright 23. A strip of insulation 34, of a size to constitute the gap for the lower dipole, is also suitably secured to the upright 23, and the ends of the lower legs of the'sections 3| and 32are secured at the "opposite ends of the strip `34, as indicated at 35 and 36, respectively. Each of the sections 3|" and 32 may have clamped to the upper and lower legs thereof an insulated support 31, withthe lower ends of those supports connected, by means of a V-shaped brace` 38, to the upright 23.

It .will be' appreciated that the illustrated methods of .mounting the dipoles 2| and 22 upon uprights 23 are purely by way Yof example and that other mounting arrangements maybe provided-Attention is called to the fact, however, that while the dipoles 2| and 22 are shown as parallel, the suggested mounting arrangements permit the dipoles to be adjusted around the upright 23 so as to occupy different angular positions with respect Yto each other, and thus the user may place the respective dipoles in that position which produces the best signal reception in accordance with the conditions in the particular locality and,v for the direction of the signals which the user `desires to receive most eiiicaciously.

The upper and lower dipoles 2| and 22 are shown as connected to the conductors of a twowire transmission line 4|, but any other type of transmission line may be used. The connections consist of pairs of feeder links 42 and 43. One flattened end of each link 42 overlies each end 21 of the dipole 2| and is secured thereto by the same bolts or rivets which secure the ends 21 to the insulation 26. The lower ends 45 of the links 43 are secured to the insulation strip 34 by the same-bolts or rivets 35 and 36 which mount the ends-of the lower dipole 22 upon that insulation, and the free ends of the links 42 and 43 are overlapped in the space between the dipoles, with bolts or rivets 46 joining together the respective pairs of links and the opposite sides of the transmission line 4|. K' y In the system/of Figs. 1 to 3, a pair of frequency4 dividers 41 are connected between the dipole 22 and the transmission line 4|, which dividers servemainly to prevent undesirable inter- 4 actions between the dipoles 2| and 22 and to greatly improve the directivity pattern of the assembly. Various arrangements of these frequency dividers may be used, some of which will be described, and various constructions of dividers may be devised. Some constructions suitable for. thisl purpose are illustrated in our copending application, Serial No.` 437,712, led April 4, '1942,' now Patent No. 422,458; issued y June 17, 1947, and a suitable construction also is illustrated in Fig. 4.

, Dividers 41 comprise a coil 5|, which may or may not be wound upon an iron core 52, and the winding may be such as to have sufficient distributed capacity, or a separate condenser 53 may be used. The coil and condenser are enclosed in an insulating tube 54, which is of a size and length to also receive the respective ends of the tubes 43 and 43A, the whole being held in assembled relation by means of screws 55. The lead wires 56 of the coil and condenser carry lugs 51 which are engaged by the screws 55, thus completing the circuit between the divider elements and the feeder'links. It will be understood that the interior of the tube 54 may be filled with wax or other compounds to protect the components from the effects of weather.

The arrangement of inductance and capacitance may-be in series or in parallel circuit dependinguponparticular conditions, as will be demonstrated. In the circuit of Figs. 1 to 3, the parallel connected coil and condenser or capacity isused, and ther arrangement isv such that the dividers are `vanti-resonant at approximately the inean'frequency for the bandfor which the upper dipolejZlrris designedLwhile all frequencies outside that band'will pass through the dividers without substantial attenuation. In the example being used, the dividers are arranged to be antiresonant at megacycles, and the electrical effe'ct ofthe dividers for frequencies in the 174-216 megacycletband is as though only the dipole 2| were'connected tothe lead-in 4|.

As is well'known, the directivity of an antenna is very important in ytelevision and in some other usesin the high frequency, and the ultra high frequency, channels. A dipole, when operated at its fundamental frequency, or in the vicinity of.

that frequency, normally has a pattern resembling the figure 8, and it is very desirable that at least that pattern be maintained in antenna systems such as described in this application. The directivityA pattern of the antenna system of Figs. 1 to.3 and the effect of the dividers 41 thereuponwill be understood by reference to the horizontal directivity patterns shown in Figs.` 5 and 6.

In Fig. 5 the solid line graph- 6| illustrates the horizontal pattern of the antenna system at 60 megacycles, which is approximately the mid-frequency of the 44-88 megacycle band to be received'by the lower dipole 22, and it will be noted that it' approximates the normal pattern of a dipole designed for that frequency, notwithstanding the presence of the dividers 41. The broken line "graph |2-illustrates the'horizontal pattern of theantenna system at megacycles, or the approximate mid-frequency of the 174-216 band of frequencies for which the upper dipole 2| is desig-ned, again with the dividers 41 in the circuit. It will be noted that the fmaxima of the two graphs coincide in a direction perpendicular to the-plane of the dipole.

Fig.A 6 lillustrates the horizontal pattern of the dipoles l2| and 22 with the dividers shortcircuited to show the-effects of the lack of dividers. Here animee itwill rbe noted'that thagraph 63, illustrating thez-.pattern of the dipole 22 at t0 megacyclesvis onlye :slightly differentVv 'from the .corresponding graph 6|. in Fig.'.,5.. On ythe other hand. the graph 6&,1 whichrepresents the pattern of the system at 190 megacycles, does not resemble'the desirablegure .8, but has four major lobes, which are more or lessv equispaced and do not coincide with thegraph 53, andY only minor lobes in the axis of the graph E3." A11-antenna having such a= pattern n is highly f objectionable, especially for television reception.

A comparison of the curves 64 and 62"illus trates graphically the eiect of the dividers ill? on the horizontal pattern of the antennaesyste'm of Figsi-l to 3 when operatingat 190v megacycles.

Thosf'divid'ers being connected in the feeder' links between the dipoles andthe transmission line",V vand designed tobe'fantif-resonantjat' 196 megacycles Y and to have a* high impedance in the entire zbandibetween 174' and 1216megacycles effectively isolate *the large dipole -22 from {thetrans'mission line so thatsignals'are receivedcn y* from thesmall dipole as lif fthe-large dipolewere non-existent. Likewise', the dividers'willhavel a high impedance vcharacteristic to` the harmonic of "thenllonger antennajthat is in the vicinityoff 190 megacycles. The result is :that the pattern of the y multiple dipole type of antennasystex'n at 190 rn'egacycles and,y by;4 reference; that of the l74-2l6rnegacycles band',` is altered troni the unl' desirable and unsuitable oneshow'nfi'n Figa ifto the desirable fand l useful formshown in yFig 5. Moreover, thesedividers have low impedance in theV low frequency bandand therefore the sfatisff factory usefulness of 'the-systeminreceiving sig'- ri'als'- in the 444-108 megalcycle bands is preserved.

vlnevertingto"reception of'television signals, 'it is *known thatv at times *itisl desirable touse ya reflector and/ or a director, Witnadipole." It will be evident that the well known varrangements fof reflector or director may be used in conjunction Withthe dipoles 2| vand 22,A and willbe used with the systems ofv this application underv the samey circumstances and for the same reasons asthey;

are used With'single dipole antennas. Y*

Fig. 7 illustratesa'system according -to this invention in Whicha different forni of `dipolefis usedand in which reflectors are added to improvek the directivitypattern `'andtheresponse of the system. Iny this systemyshorterydipole 'El and longer dipole l2 are mounted on: a support i3.

' Also-mounted on thev support is the rod type of reflector 'IG for the shorter dipole anda loepA type oi' reflector 'l5 for the longer dipole.

'Considering the details of construction; the support 13 has a coupling 16 adjustably mounted intermediate its lengthQlfrom which Iarms TI and 9| in'its upper edge and respectively extending inwardly from the opposite sideiedges the block.l The central ungrooved portion' 92 denes the gap for the lower dipole 12. The ends'of'the 'Elli '7o' along its lower edge and a similarpair of grooves 6? upper-and lower legs of the respective :dipole arms. |34` andz'are received inthe appropriate pairs of v'grooves 88 a'ndzlv and arerespe'ctively con# nected .together by the bolts 93 andi-BSA.- .which extend through the block 'I9 and thus mount the' arms. upon the block. l Y

y'The reflector. l5 comprisestwo straight-central sections 94 andy U.shaped end- pieces 95 and 96 which are telescopicallj'rv received in the-straight sections 94 and suitably clamped thereto in"adjusted position. `The block" 8| y has continuous grooves alongits upper and lower edgesVwhich receive the straight lsections Aihk-the' assembly` being'bolted"together,l asbyb'eltg'l. v-

Atits upper end the standard 13 issurmo'u'nted by a T-shaped 'coupling lill, which supports horl'` zontal-'arms |2 andI i631 r`.llt'itsout'er' end-the arm'l d2 .has'niounted l thereon a block' I'illlV which is-sirnilarinconstruction7 to theblocl; '19.1Y TheLv pairs 'fofupperf'andf lowergroovs Hlrespectivelyfreeeivethe lenclsofVv loops G5 'and |91; come: prisl'ng tlie; arms fori dipole 1 l, and l theY loops'. are' respectively closed by 'throughI- boltsl Idil which; secure `the sametothe 'block-loll." 1 "f Elfiearrn` I'B'Ssupportsat itsfouter end a-'centralf tube |239 Aineachvr endo4 which'lare adjust-ably mounted rod Vsections lili with suitable clampingar'rangement's for the telescopingsections; ene" abling the-portions l l-tohe-rnoved in andvout' according tothedesired lengthpffthe-reflect i '4i'- The dipoles 'll and l2 are joined together nd toa vtransmission' line by feeder linlsrwh'i'ch comprise-avvpair of tubes' l2- and |.l`3,`respe`ctively fastened at their/uppercase uq-the oppisitearms- Gfl the"dpbl`l, a. 'pal tubesAv l-'Uv arld'f'l |25; respectively --f astened'f at f theirY l'ower. f ends to the? arms Q land 586 of. the-'dipole "|'2f,"a`n'dv a' pair vof dividers |15. The ends of the tubes-ll l2 andillll` extend' into and are:` fastened f'toithe' insulated" casing 'of one 'ofthe dividers HSL-which maj/:be similari inV constructionf tol the divider l1 shown in-"Irig zljfand tubes |1ifafndf| l5 farereceivedim the insulatedf'tubelojfithefsecond"divider H152 also similar in construction-to tliedivider 4i: YIn this case, the endslof'tlie wiresfo'f-thetransmission lille H povded With4 lgS` HVWhoh-l? secured respectively to'one end of eachfdivi'der cur the dividers" ne to the links u2 analizares'pectively. Ther ends of the tubesfi |2-'-||5`a re` flattened and are secured to the' respective dip'olef arms-by the same bolts' which secure the armste" thefbloclsf'landloll. l, u *t vThe circuit diagrampf `the antenna syst -shptvn innig, 9 illustrates @system retval-carne" dipoles-are spacedapart in a horizontalt plane( and alsor the use of dividers: which -alreuanti resonant "at a` certain'v Afrequency and` other dividers which-'arere'sonantat a certain 'frequency but'bothtypes of dividers permit signals of otherv fre'quiencies to pass, according to the de'sign of 1 and 'l 22 are joined '5to transmission lineV |23 by ance for ythe frequencies fin Ythe, f |14-2I B vmega-` A cycle band. At the saine time, the condenser |28v is sufficiently small so that at 4||'-884rnega= cycles, the `series reactance of the 'divider is high'- enough to's'ub'stantially isolate the'smallf'dipole'j |2| from the rest of the antenna system. While meansY of the'fscrews; (not showni' which' also; sel/ it is true that as the frequency approaches 175 megacycles, these dividers begin to cease functioning elliciently, in the example given in this case,. the highest frequency to be received in the lower band is 108 megacycles (i. e., the FM band of 88-108 megacycles), so that the inefficiency occurs well within the band where this particular antenna is not designed to function.

-The dividers |3|, in the links |24, comprise an inductance |32 wound with sufcient distributed capacity (although a, separate condenser may be used) to make its natural period about 195 megacycles. at which frequency the divider may be said to present an infinite impedance; and the impedance remains high throughout the 174-216 megacycle band, so that the large dipole |22 is practically open-circuited for all frequencies within that band, and is rendered practically non-existent for signals within that band. The dividers |26 and |3| in the respective feeder links to the transmission line enable the entire system to function with a proper directivity pattern for the respective bands for which the dipoles |2| and |22 are designed. Alternatively, it will be understood that a divider of the series type, i. e., in which the inductance and capacitance are arranged in series circuit relation, may be inserted directly in either dipole, and the divider will be tuned to the frequency at which it is desired to effectively render the dipole opencircuited.

Fig. is illustrative of a circuit arrangement wherein a third dipole is added to the system inorder to receive another frequency band, for example. the band of 400-450 megacycles. In this case, the dipoles |33 and |34 correspond to the dipoles 2| and 22 of Figs. 1 to 3, and a third dipole |35, of a size to cover the additional frequency band, is also provided, all three dipoles being connected to the transmission line |36. In this case, the feeder links |31 from the dipole |34. and the feeder links |38 from the dipole |33 are joined together at mid-points |39. 'I'he links |31 are each provided with a divider 4| which may comprise inductance and capacitance arranged to be anti-resonant at the third harmonic of the fundamental frequency of dipole |34 or for the mid-frequency of the band covered by the dipole |33 and of high impedance for that entire band. Feeder links |42 extend from mid-points |39 to the transmission line conductors |36 andare provided with dividers |43. The latter dividers comprise suitable inductance and capacitance arranged to be anti-resonant for the mean frequency of the dipole |35 and to have high impedance for the band of that dipole and low reactancevfor the frequency bands of dipoles 33 and |34.

Fig. 11 illustrates an addition which may be made under certain circumstances to an antenna system yof the type shown in Fig. '1. In this case the respective parts of the arms of the dipoles 1| and 12 are Vbrought to a point, indicated at |46 and |41, to which points the feeder' links ||2||5, inclusive, are joined, as shown, and the feeder links are also provided'with dividers v| I6. This method of joining the branches of each arm is an alternate arrangement to that shownin Fig. 7, which some users may prefer.

In the illustration of Fig. 11, an inductance |43 is connected between the arms of the shorter dipole 1|, or between the feeder links ||2and 3. The circuit including the inductance |48 and the dipole 1| and its leads is constructed to be anti-resonant at one hundred ninety-five megacycles (the midpoint of the band of frequencies for which the dipole 1| is designed in the examples used in this case) which neutralizes the capacitive reactance ofthe separate antenna arms 1| and the associated leads. In tests it was found that the addition of the inductance |48 also increased the response of the system for frequencies in the band of eightytwo to one hundred eight megacycles, which includes the last channel presently assigned to broadcast of television signals and all those channels assigned to frequency modulation broadcast.

It is believed that it is obvious that a plurality of folded or other dipoles designed to receive the same frequency bands may be connected to a common transmission line, as, rfor example, in order to obtain a higher gain in the antenna, or to make it omni-directional. When several such dipole arrays lare to be joined to a common transmission line, a set of shunt and/or series type dividers should be included in the feeder connections between the respective dlpole arrays and the transmission line, the proportioning of the elements of the dividers being such as to render the particular dipole or dipoles effective or ineffective as may be desired.

Throughout all of the foregoing disclosures, there has been illustrated a flexibility in devices but not in principles whereby two or more dipoles may be connected to a common transmission line and automatically be effective to receive selected signals with the exactness required for good television reception and for high delity frequency modulation reception.

It is obvious that other modifications maybe made in the arrangement and location of parts within the spirit and scope of our invention, and such modifications are intended to be covered by the appended claims.

We claim:

1. An antenna system comprising, a pair of separate dipoles respectively constructed and arranged to receive signals in a band of wave lengths, the bands being separated from each other, the dipoles being spaced with respect to each other, and means interconnecting said dipoles and including impedance means selected to have a maximum response at a frequency corresponding to substantially the mean wave length of one of said dipoles.

2. An antenna system comprising, a short dipole and a long dipole arranged to .provide .substantially maximum. response for dierent bands of frequencies, the dipoles being spaced with respect to each otherl and means interconnecting said dipoles and including inductance and capacitance having values and arranged to provide maximum impedance to a harmonic frequency of the long dipole which is substantially the mean frequency of the short dipole.

3. An antenna system comprising, a pair of dipoles of different lengths arranged to provide substantially maximum response for different bands of frequencies, one dipole being approximately three times the length of the other dipole. the dipoles being spaced with respect to each other, and means interconnecting said dipoles .and including inductance and capacitance hav-A ing values and arranged to provide a maximum response at the third harmonic of substantially the mid-frequency of the long dipole.

4. An antenna system adapted to be mounted .upon an upright and comprising, a plurality of dipoles respectively constructed and arrangedv to provide ksubstantially maximum response for a b and of frequencies, the bands of frequencies being separated from each other, means for mounting the dipoles upon said upright soy that at least oney of said dipoles may occupy a horizontally angular position which is different from others of said dipoles, a common connection to which said dipoles are connectedl'and frequency responsive means interposed in circuit between one of said dipoles andY said connection, said meansV having selected values to have a high impedanceat the frequencies in the bandof frequenciesl of vanother 4 of said dipoles and of negligibleY effect in saidfcircuit at lother frequencies# whereby each ofsaid dipoles will function to deliver signal voltagesto said transmission line independently of thev remainder of said dipoles.

' 5. Anantenna system comprisingl an upright, a 'pair of dipoles mounted thereonvand respectively constru'ctedand arranged to" provide substantially'maximum kresponse for a; band vof frequencies, the vbands being separated from'v each other and the dipolesfbeing' spaced apart", a common transmission line for said dipoles, and means interconnecting said dipoles and transmission line, said means including first frequency responsive means which are anti-resonant at 'a selected narrow band'of frequencies, and second frequency responsive means which are resonant at another Aselected narrow band of frequencies, said frequency responsive means being of negligible electrical effect in the circuit of said system at frequencies within the other bands of frequencies for which said system is designed.

6. An'antenna system comprising anupright, a pair of dipoles mounted thereon and respectively constructed and arranged to provide substantially maximum response for a band of frequencies, the bands being separated from each otherand the dipoles being spaced apart,

and connections from said dipoles to .suitable l signal receiving apparatus, saidconnections including a common transmission line, rstbfrequency responsive means which .have ahigh impedance at a selected frequency, and. second frequency responsive means which have" vauhigh impedance at another lselected frequency', Lsaid selected frequencies beingchosento prevent interference between said dipoles and of negligible electrical effect in the'circuitof lsaid system at other frequencies. y.

47. antenna system comprising an upright, a pair of dipoles mounted thereon and respectively constructed and arranged to provide substantially maximum response for a band of frequencies, the bands being separatedk from each other and the dipoles being in substantially the same horizontal plane and spaced apart, a common transmission line between said dipoles and suitable signal receiving apparatus, first feeder connections from one of said dipoles to said transmission line, said first connections .including frequency responsive means having high impedance for a selected narrow band of frequencies within the bands of frequencies for which said dipoles are responsive and of negligibleelectrical effect in the circuit of said system at other frequencies, and second feeder connections from the other of said dipoles to said transmission line, which latter connections include frequency responsive means which have a low impedance for .a selected narrow band of frequencies within the bands of frequencies for 10 which'said dipoles are responsive Aand of negligible electrical effect in the circuit of said system vat other frequencies.

8. An antenna system comprising an upright, a plurality of dipoles mounted thereon and respectively constructed and arranged to provide substantially maximum response for .a band of frequencies, the bands being separated lfrom each other and thedipoles being spaced apart. a pair of terminals for connection of said'dipoles and a suitable signal receiver, and means in circuit between one of. said dipoles and said terminals and including first frequency responsive `V 'means having high impedance for a selected' band Aof frequencies within theband of frequencies'fo'r which one of said dipoles is responsive, and means connecting another of said' dipoles to said terminals and including second frequency responsive means which are resonant for a selected frequency within the band offrequencies of another of said dipoles, said second frequency responsive means being of negligible electricaleffect in the circuit of said system vat other frequencies.

9j An antenna system comprising an upright, apair of dipoles mounted thereon and respectively 'constructed and arranged to provide substantially vmaximum response for a band of frequencies, the bands being separated from each other and the dipoles being spaced apart, a' 'common transmission line between said dipoles andfa suitable signal receiver, means connecting one "of said dipoles to said transmission line and including rst frequency responsive means having high impedance for a selected narrow band of .frequencies and of negligible electrical eifect in the circuit of said system at other frequencies, and4 second frequency responsive means mounted in ccnnectionwith the second dipole and arranged to electrically interrupt the circuit of said second dipole at a selected frequencyv and of negligible electrical effect in the circuit of said system at other frequencies.r

4 10. An antenna system comprising a plurality of separate and spaced apart antennas ofthe dipole type each of different length to receive Y different bands of frequencies which are separated from each other, a common transmission frequency'band of the other antenna, and other` connections from said vinterconnections to said transmission line and including electrical means having values for preventing said pair of .antennasffromv transmitting signalling voltages in the frequency band of a third antenna.

1l. An antenna system comprising a plurality of separate and spaced apart antennas of the dipole type each of different length to receive different bands of frequencies which are separated from each other, a common transmission line from said antennas to suitable signal receiving apparatus, interconnections between a pair of said antennas and including inductance and capacity having selected values arranged to have a high impedance for the band of frequencies of one of said pair of antennas, and other connections from said interconnections to said transmission line and including inductance and capacitance having selected values arranged quencies of a third antenna. t

12. A multi-band antenna system comprising a pair of separate and spaced apart antennas of the dipole type at least one of said antennas comprising a pair of arms arranged on opposite sides of a gap, the antennas being of different lengths to receive different bands of frequencies, a common connection for said antennas and suitable signal apparatus, rst frequency responsive means in circuit between the other of said antennas and said common connection, said first means having a high impedance at frequencies within the band of frequencies of' said one antenna,` and second frequency responsive means electrically connected across the gap of said one` antenna, said second means having a selected impedance and arranged to increase the signal response of said system in a selected portion of the band of frequencies for which the other antenna of said pair is responsive.

13. A multi-band antenna system comprising a support, a pair of separate and spaced apart antennas of the dipole type mounted thereon and at least one of said antennas comprising a pair of arms arranged on opposite sides f a gap, the antennas being of different lengths` to receive different bands of frequencies which are separated from each other, a common connection between said antennas and suitable signal apparatus, frequency responsive means in circuit with said antennas and said common connection and arranged so that said system provides substantially maximum response for each of said frequency bands, and an inductance electrically connected across the gap of said one antenna and arranged to be anti-resonant at approximately the mid frequency of the band of fre-V quencies for which said one antenna is responsive and to have an inductive reactance in the circuit at frequencies within the band of frequencies for which the other antenna of said pair is responsive.

14. In an antenna system comprising a pair of interconnected antennas of the dipole type having portions respectively formed of tubing and connected to a common down lead, a pair of impedance devices comprising inductance and capacitance having selected values and being arranged to have high impedance for the frequencies for which one of said antennas responds,

said devices also comprising rigid insulating means having end portions of a size to interiit with said tubing respectively, and terminal con'- nections from said inductance and. capacitance and adapted to be connected to said tubing whereby the circuit of the antenna system will be continued through said devices.l

15. A network for use in an antenna system comprising a pair of interconnected antennas 0f the dipole type formed of tubing and con- CFI nected to a common down lead, said network comprising a pair of impedance devices. each device comprising inductance and capacitance having opposite terminal members to which different portions of said tubing are to be connected, rigid insulating means having end portions of a size to interflt with said tubing respectively, said inductance and capacitance having selectedvalues and being arranged to have high impedance for the frequencies for which one of the antennas responds.

16. A multi-band antenna system comprising a pair of separate and spaced apart antennas of the dipole type adapted to be mounted upon an upright and at least one of said antennas comprising a, pair of arms arranged on opposite sides of a gap, the antennas being of diiferent lengths to receive different bands of frequencies which are separated from each other, a pair of terminals vto which said antennas and suitable signal apparatus are adapted to be connected. frequency responsive means in circuit between one of said antennas and said terminals, said means having a high impedance at frequencies within the band of frequencies of the other of said antennas,` and an inductance electrically connected across the terminals and having a selected impedance at frequencies for which said system is responsive and arranged to increase the signal responsive in a selected portion of the frequencies for which said system is responsive.

ERNEST V. AMY. JULIUS G. ACEVES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,102,426 Lindenblad Dec. 14, 1937 2,110,159 Landon Mar. 8, 1938 2,168,857l Barbour Aug. 8, 1939 2,229,865 Morgan Jan. 28, 1941 '2,248,335 Burkhart July 8, 1941 2,268,640 Brown Jan. 6, 1942 2,281,429 Goddard Apr. 28, 1942 2,282,292 Amy May 5, 1942 2,283,914 Carter May 26, 1942 2,297,329 Scheldorf Sept. 29, 1942 2,299,218 Fener Oct. 20, 1942 2,380,519 Green July 31, 1945 2,419,311 Bigue Apr. 22, 1947 2,481,801 Valach Sept. 13, 1949 FOREIGN PATENTS Number Country Date 520,849 Great Britain May 6. 1940

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